以下是基于商业智能/报告专家和战略/规划经理角色的评论:

I agree with Larry's direction above. IMHO, It's not so much over engineered, some things just look a little out of place. To keep it simple, I would tag client directly to a Company ID, Department Description, Division Description, Department Type ID, Division Type ID. Use Department Type ID and Division Type ID as references to lookup tables and internal reporting/analysis fields for long term consistency. Packs table contains "Credit" column, shouldn't that actually be tied to the Client base table so if they many packs you can see how much credit owed is left for future classes? The application can take care of the calc and store it centrally in the Client table. Company info could use many more fields, including the obvious address/phone/etc. information. I'd also be prepared to add in D&B "DUNs" columns (Site/Branch/Ultimate) long term, Dun and Bradstreet (D&B) has a huge catalog of companies and you'll find later down the road their information is very helpful for reporting/analysis. This will take care of the multiple division issue you mention, and allow you to roll up their hierarchy for sub/division/branches/etc. of large corps. You don't mention how many records you'll be working with which could imply setting yourself up for a large development initiative which could have been done quicker and far fewer headaches with prepackaged "reporting" software. If your not dealing with a large database (< 65000) rows, make sure MS-Access, OpenOffice (Base) or related report/app dev solutions couldn't do the trick. I use Oracle's free APEX software quite a bit myself, it comes with their free database Oracle XE just download it from their site. FYI - Reporting insight: for large databases, you typically have two database instances a) transaction database for recording each detailed record. b) reporting database (data mart/data warehouse) housed on a separate machine. For more information search google both Star Schema and Snowflake Schema.

的问候。

I want to address only the concern that joining to mutiple tables will casue a performance hit. Do not be afraid to normalize because you will have to do joins. Joins are normal and expected in relational datbases and they are designed to handle them well. You will need to set PK/FK relationships (for data integrity, this is important to consider in designing) but in many databases FKs are not automatically indexed. Since they wil be used in the joins, you will definitelty want to start by indexing the FKS. PKs generally get an index on creation as they have to be unique. It is true that datawarehouse design reduces the number of joins, but usually one doesn't get to the point of data warehousing until one has millions of records needed to be accessed in one report. Even then almost all data warehouses start with a transactional database to collect the data in real time and then data is moved to the warehouse on a schedule (nightly or monthly or whatever the business need is). So this is a good start even if you need to design a data warehouse later to improve report performance.

我不得不说你的设计对于一个计算机科学的大一学生来说是令人印象深刻的。

以下是基于商业智能/报告专家和战略/规划经理角色的评论:

I agree with Larry's direction above. IMHO, It's not so much over engineered, some things just look a little out of place. To keep it simple, I would tag client directly to a Company ID, Department Description, Division Description, Department Type ID, Division Type ID. Use Department Type ID and Division Type ID as references to lookup tables and internal reporting/analysis fields for long term consistency. Packs table contains "Credit" column, shouldn't that actually be tied to the Client base table so if they many packs you can see how much credit owed is left for future classes? The application can take care of the calc and store it centrally in the Client table. Company info could use many more fields, including the obvious address/phone/etc. information. I'd also be prepared to add in D&B "DUNs" columns (Site/Branch/Ultimate) long term, Dun and Bradstreet (D&B) has a huge catalog of companies and you'll find later down the road their information is very helpful for reporting/analysis. This will take care of the multiple division issue you mention, and allow you to roll up their hierarchy for sub/division/branches/etc. of large corps. You don't mention how many records you'll be working with which could imply setting yourself up for a large development initiative which could have been done quicker and far fewer headaches with prepackaged "reporting" software. If your not dealing with a large database (< 65000) rows, make sure MS-Access, OpenOffice (Base) or related report/app dev solutions couldn't do the trick. I use Oracle's free APEX software quite a bit myself, it comes with their free database Oracle XE just download it from their site. FYI - Reporting insight: for large databases, you typically have two database instances a) transaction database for recording each detailed record. b) reporting database (data mart/data warehouse) housed on a separate machine. For more information search google both Star Schema and Snowflake Schema.

的问候。

不。看起来你设计得很细致。

我认为在你的设计中，国家和公司实际上是同一个实体，城市和部门也是如此。我将去掉国家和城市表(以及Cities_Has_Departments)，并在必要时向公司表添加一个布尔标志IsPublicSector(如果除了简单的Private Sector / PublicSector之外还有其他选择，则添加CompanyType列)。

Also, I think there's an error in your usage of the Departments table. It looks like the Departments table serves as a reference to the various kinds of departments that each customer division can have. If so, it should be called DepartmentTypes. But your clients (who are, I assume, attendees) do not belong to a department TYPE, they belong to an actual department instance in a company. As it stands now, you will know that a given client belongs to an HR department somewhere, but not which one!

换句话说，客户机应该链接到您称为Divisions_Has_Departments的表(但是我将简单地称之为Departments)。如果是这样，那么如果您想在数据库中使用标准引用完整性，就必须将Cities分解为division，就像上面讨论的那样。

大多数事情都已经说过了，但我觉得我可以补充一点:年轻的开发人员在一开始就有点过多地担心性能，这是很常见的，而你关于连接表的问题似乎正朝着这个方向发展。这是一种名为“过早优化”的软件开发反模式。试着把这种反射从你的脑海中赶走:)

还有一件事:你真的需要“城市”和“国家”表吗?难道在部门表中有一个“城市”和“国家”列不足以满足您的用例吗?例如，您的应用程序需要按城市和城市按国家列出部门吗?

以下是关于你问题的更多答案:

1)对于第一次遇到这种问题的人来说，你说得很对。我认为到目前为止，其他人在这个问题上的建议几乎涵盖了这个问题。好工作!

2 & 3)性能的下降很大程度上取决于为特定的查询/过程设置和优化正确的索引，更重要的是记录的数量。除非您的主表中有超过一百万条记录，否则您似乎已经走上了一条足够主流的设计道路，在合理的硬件上，性能不会成为问题。

That said, and this relates to your question 3, with the start you have you probably shouldn't really be overly worried about performance or hyper-sensitivity to normalization orthodoxy here. This is a reporting server you are building, not a transaction based application backend, which would have a much different profile with respect to the importance of performance or normalization. A database backing a live signup and scheduling application has to be mindful of queries that take seconds to return data. Not only does a report server function have more tolerance for complex and lengthy queries, but the strategies to improve performance are much different.

For example, in a transaction based application environment your performance improvement options might include refactoring your stored procedures and table structures to the nth degree, or developing a caching strategy for small amounts of commonly requested data. In a reporting environment you can certainly do this but you can have an even greater impact on performance by introducing a snapshot mechanism where a scheduled process runs and stores pre-configured reports and your users access the snapshot data with no stress on your db tier on a per request basis.

所有这些都是为了说明根据所创建的db的角色不同，所采用的设计原则和技巧可能会有所不同。我希望这对你们有帮助。